如何在没有用户输入的情况下自动返回主菜单？

“主菜单”是此处的位置System.out.print("enter letter P T L S A or Q");。用户输入其姓氏后，控制台应自动返回到第一个System.out.print语句，即菜单。我如何将其设置为这样？

class myOwnTryAginLoopThatWorks{
    public static void main (String [] args){
        Scanner console = new Scanner(System.in);
        boolean valid;
        char choice = '\0';
        String persnr;
        do{
            valid = true;
            System.out.print("enter letter P T L S A or Q"); //menu
            String input = console.nextLine();
            if (!isValid(input)){
                valid = false;
                System.out.print("You did not enter the correct menu option, ");
                if (input.length() != 1) {
                    System.out.println("and your input length is too long (must be 1 character long), ");
                    valid = false;
                }
            }
            choice = input.charAt(0);
        }while(!valid);

        switch (choice) {
            case 'P':
                    do {
                        valid = true; 
                        System.out.print("Enter persnr in the format of (YYYYMMDD): ");
                        try {
                            persnr = console.nextLine();
                            if (!persnr.matches("[1-9]{1}[0-9]{7}")) {
                                throw new IllegalArgumentException("You printed wrong format, try again");
                            }
                            System.out.println("Processsing...");
                        } catch (IllegalArgumentException e) {
                        System.out.println(e.getMessage());
                        valid = false;
                        }
                    } while (!valid);
                    break;
        }

        System.out.print("enter first name ");
        String firstName = console.nextLine();
        System.out.print("enter surrname ");
        String surName = console.nextLine();

    } 

    public static boolean isValid (String n){ 
        switch(n){
            case "P":
            case "T":
            case "L":
            case "S":
            case "A":
            case "Q":
                    return true;
            default:
                    return false;
        }
    }    
}

问题来源：Stack Overflow